Message modality and source credibility can interact to affect argument processing

Research extends previous modality and source cue studies (Andreoli & Worchel, 1978; Chaiken & Eagly, 1983) and the heuristic processing interpretation (Chaiken, 1987) by manipulating argument quality. College students (N = 243) were randomly assigned by class to an argument quality (strong/weak) by source attribute (high/low credibility) by modality (print, audio, video) factorial experiment under conditions of moderate topic involvement. The print mode enabled systematic processing leading to an argument main effect on attitude change and cognitive responding. Contrary to the heuristic interpretation of previous research, the data showed an argument quality by source attribute interaction in audio and video modes. Manipulation checks, attitude change, and cognitive responses indicated that source credibility functioned as both a cue and an elaboration moderator, leading to greater argument processing in the latter case. Results support a multiple capacities conceptualization.